UNIVERSITY  OF  CALIFORNIA  PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 
AGRICULTURAL  EXPERIMENT  STATION 


Further  Proof  of  the  Cause  and  Infectiousness 

of  Crown  Gall 

By  CLAYTON  O.  SMITH 


BULLETIN  No.  235 

(BERKELEY,  CAL.,  DECEMBER,  1912) 


Friend  Wm,  Richardson,  Superintendent  of  State  Printing. 

sacramento,  california 

1912 


Benjamin  Ide  Wheeler,  President  of  the  University. 

EXPERIMENT    STATION    STAFF. 

T.  F.  Hunt,  D.Agr.,  Director. 

E.  J.  Wickson,  M.A.,   Horticulturist. 

E.  W.  Hilgard,  Ph.D.,  LL.D.,  Chemist   (Emeritus). 
W.  A.  Setchell,  Ph.D.,  Botanist. 

Leroy  Anderson,  Ph.D.,  Dairy  Industry. 
M.  E.  Jaffa,  M.S.,  Nutrition  Expert. 

R.  H.  Loughridge,  Ph.D.,  Soil  Chemist  and  Physicist  (Emeritus). 
C.  W.  Wood  worth,  M.S.,  Entomologist. 

Ralph  E.   Smith,  B.S.,   Plant  Pathologist  and  Superintendent  of  Southern  California 
Pathological  Laboratory  and  Experiment  Station. 

F.  R.  Marshall,  B.S.A.,  Animal  Industry. 
J.  E.  Coit,  Ph.D.,  Citriculturist. 

H.  J.  Webber,  Ph.D.,  Director  Citrus  Experiment  Station,  Riverside. 
J.  W.  Gilmore,  M.S. A.,  Agronomist. 

A.  V.  Stubenrauch,  M.S.,  Pomologist. 
C.  F.  Shaw,  B.S.,  Soil  Technologist. 

J.  W.  Gregg,  B.S.,  Floriculturist. 

G.  W.   Shaw,   M.A.,   Ph.D.,   Experimental   Agronomist   and  Agricultural   Technologist, 

in  charge  of  Cereal  Stations. 

B.  A.  Etcheverry,  B.S.,  Irrigation  Expert. 
F.  T.  Bioletti.  M.S.,  Viticulturist. 

W.  T.  Clarke,  B.S.,  Assistant  Horticulturist  and  Superintendent  of  University  Exten- 
sion in  Agriculture. 
John  S.  Burd,  B.S.,  Chemist,  in  charge  of  Fertilizer  Control. 

C.  B.  Lipman,  Ph.D.,  Soil  Chemist  and  Bacteriologist. 

George    E.    Colby,    M.S.,    Chemist    (Fruits,    Waters,    and    Insecticides),    in    charge    of 

Chemical  Laboratory. 
H.  J.  Quayle,  M.S.,  Assistant  Entomologist. 
H.  M.  Hall,  Ph.D.,  Assistant  Botanist. 
C.  M.  Haring,  D.V.M.,  Veterinarian  and  Bacteriologist. 
E.  B.  Babcock,  B.S.,  Agricultural  Education. 
W.  B.  Herms,  M.A.,  Assistant  Entomologist. 
W.  T.  Horne,  B.S.,  Assistant  Plant  Pathologist. 
L.  M.  Davis,  B.S.,  Assistant  Dairy  Industry. 
W.  W.  Bonns,  M.S.,  Assistant  Pomologist. 

A.  J.  Gaumnitz,  M.S.,  Assistant  Agronomist,  University  Farm,  Davis. 
T.  F.  Hunt,  B.S.,  Assistant  Plant  Pathologist. 

E.  H.  Hagemann,  Assistant  in  Dairying.  Davis. 

R.  M.  Roberts,  Farm  Manager,  University  Farm,  Davis. 
J.  I.  Thompson,  B.S.,  Assistant  Animal  Industry,  Davis. 
J.  C.  Bridwell,  B.S.,  Assistant  Entomologist. 
L.  Bonnet,  I.A.,  Assistant  Viticulturist. 

F.  C.  H.  Flossfeder,  Assistant  in  Viticulture,  University  Farm,  Davis. 
M.  E.  Stover,  B.S.,  Assistant  in  Agricultural  Chemical  Laboratory. 

H  S.  Baird,  B.S.,  Assistant  Dairy  Industry. 

Walter  H.  Dore,  B.S.,  Chemist  Fertilizer  Control. 

P.  L.  Hibbard,  B.S.,  Assistant  Fertilizer  Control  Laboratory. 

C.  H.  McCharles,  M.S.,  Assistant  Agricultural  Chemical  Laboratory. 

B.  A.  Madson,  B.S.A.,  Assistant  Experimental  Agronomist. 

Walter  E.   Packard,  M.S.,  Field  Assistant  Imperial  Valley  Investigation,   El  Centre 
S.  S.  Rogers,  B.S.,  Assistant  Plant  Pathologist,  Plant  Disease  Laboratory,  Whittier. 

C.  O.  Smith,  M.S.,  Assistant  Plant  Pathologist,  Plant  Disease  Laboratory,  Whittier. 

E.  H.  Smith,  M.S.,  Assistant  Plant  Pathologist. 

C.  L.  Roadhouse,  D.V.M.,  Assistant  m  Veterinary  Science. 

F.  M.  Hayes,  D.V.M.,  Assistant  Veterinarian. 
P.  S.  Burgess,  M.S.,  Assistant  Soil  Chemist. 
W.  F.  Gericke,  B.S.,  Assistant  Soil  Chemist. 

J.  E.  Dougherty,  B.S.A.,  Assistant  Poultry  Husbandry. 
W.  H.  Volck,  Field  Assistant  in  Entomology,  Watsonville. 
E.  L.  Morris,  Field  Assistant  in  Entomology,  San  Jose. 

E.  E.  Thomas,  B.S.,  Assistant  Chemist,  Plant  Disease  Laboratory,  Whittier. 
A.  B.  Shaw,  B.S.,  Assistant  in  Entomology. 

G.  P.  Gray,  M.S.,  Chemist  in  Insecticides. 

H.    D.    Young,   B.S.,   Assistant   in   Agricultural   Chemistry,    Plant   Disease   Laboratory, 

Whittier. 
A.  R.  Tylor,  B.S.,  Assistant  in  Plant  Pathology,  Plant  Disease  Laboratory,  Whittier. 
W.  V.  Cruess,  B.S.,  Assistant  in  Zymology. 
J.  F.  Mitchell,  D.V.M.,  Assistant  in  Veterinary  Laboratory. 
M.  R.  Miller,  B.S.,  Assistant  Chemist  in  Insecticides. 

F.  H.  Wilson,  B.S.,  Assistant  in  Soil  Chemistry. 
W.  M.  Mertz,  Assistant  in  Pomology,  Riverside. 

Anna  M.  Lute,  A.B.,  Scientific  Assistant.  U.  S.  Dept.  of  Agriculture. 

D.  L.  Bunnell,  Secretary  to  Director. 


PURTHER  PROOF  Of  THE  CAUSE  AND  INFECTIOUSNESS  OF 

CROWN  GALL. 

By  Clayton  O.  Smith. 

The  disease  to  be  discussed  in  this  bulletin  is  one  of  the  most  wide- 
spread and  serious  troubles  known  to  plant  life,  for  while  other  diseases 
may  destroy  a  portion  of  the  tree  or  crop,  this  trouble  gradually  weakens 
and  frequently  kills  the  tree  affected.  It  is  not  the  purpose  of  this 
paper  to  discuss  the  disease  completely  or  in  detail,  but  to  present  the 
results  of  some  experimental  work  which  has  been  done  at  the  Southern 
California  Pathological  Laboratory  upon  its  cause  and  power  of 
infection. 

BRIEF  HISTORY. 

The  crown  gall  or  root-knot  has  been  long  known  in  Europe,  the 
United  States  and  Canada,  and  is  probably  world-wide  in  its  distribu- 
tion. Just  when  the  first  published  account  of  it  was  printed  we  do  not 
know,  although  it  was  probably  fifty  to  seventy-five  years  ago.  There  is 
no  uniformity  of  opinion  among  plant  pathologists  as  to  where  this 
disease  originated.  Some  authorities  say  it  came  from  China  or  some 
country  of  Asia.  From  our  own  observations,  however,  it  seems  to  be 
without  question  native  to  many  of  the  soils  of  our  country,  and  this 
appears  to  be  especially  true  of  California,  since  there  are  numerous 
instances  of  the  occurrence  of  crown  gall  in  nurseries  on  land  where 
trees  have  never  been  grown  before. 

Crown  gall  was  first  extensively  studied  by  J.  W.  Tourney,1  who  at 
that  time  was  associated  with  the  Arizona  Experiment  Station.  He 
showed  the  pathogenic  nature  of  the  disease  by  inoculating  soil  with 
minced  galls.  He,  made  cultures  from  the  affected  tissue  and  isolated  a 
low  form  of  plant  known  as  a  myxomycete  or  slime-mold.  The  number 
of  his  inoculations  was  not  sufficient  to  be  very  conclusive,  and  subse- 
quent work  has  shown  the  disease  to  be  due  to  a  species  of  bacterium. 

In  1897  Cavara,2  an  Italian  investigator,  made  cultures  from  knots 
of  grapes,  and  succeeded  in  isolating  a  species  of  bacterium  that  pro- 
duced knots  from  his  artificial  inoculations  on  two  varieties  of  European 
grapes.  His  study  and  description  of  the  organism,  so  far  as  they  went, 
leave  little  doubt  that  he  had  found  the  true  cause  of  the  trouble. 

In  1903,  Dr.  George  G.  Hedgcock,3  while  studying  the  knot  of  the 
grape,  isolated  a  bacterial  organism  producing  a  white  colony,  but  lost 
the  cultures  in  transit.  In  1904  he  again  isolated  several  kinds  of 
organisms  from  grape  galls ;  one  of  these  was  similar  to  the  one  of  1903 
and  produced  knots  when  puncture  inoculations  were  made  in  grapes. 

Arizona  Agricultural  Experiment  Station,  Bulletin  No.   33. 

2Abstracts  and  Summary  given  in  U.  S.  Department  of  Agriculture,  Bureau  of  Plant  Industry,  Bulletin 
No.   213. 

3U.  S.  Department  of  Agriculture,  Bureau  of  Plant  Industry,  Bulletin  No.  183. 


532 


UNIVEKSITY    OF    CALIFOKNIA EXPERIMENT    STATION. 


Dr.  E.  F.  Smith  and  Dr.  C.  0.  Townsend,  of  the  Bureau  of  Plant 
Industry,  from  1904  to  1906  gave  some  attention  to  the  study  of  gall  on 
the  Paris  daisy,  Chrysanthemum  frutescens,  and  were  successful  in 
isolating  a  pathogenic  bacterial  organism  with  which  they  could  produce 
the  gall  at  will,  if  given  certain  favorable  conditions  of  plant  life.     The 

organism  was  called  by  them  Bac- 
terium tumefaciens.  Much  subse- 
quent work  has  been  done  by  Dr. 
Smith  and  his  associates,  showing 
that  this  organism  is  capable  of 
causing  knots  on  a  great  number  of 
different  host  plants.1  This  same 
organism  has  also  been  isolated 
from  galls  found  on  quite  a  number 
of  different  plants. 

Plant  pathologists  have  been 
very  slow  in  attempting  a  thorough 
investigation  of  this  disease  until 
within  recent  years,  and  this  may 
be  readily  accounted  for  because  of 
the  following  reasons:  (1)  Pro- 
fessor Tourney  published  quite  a 
complete  paper  on  the  subject,  and 
this  would  naturally  discourage 
an  investigator  from  repeating  his 
work.  (2)  The  seeming  hopeless- 
ness of  finding  a  successful  method 
of  preventing  the  disease  would 
cause  workers  to  study  first  those 
diseases  that  could  be  more  easily 
controlled.  (3)  The  early  workers 
in  the  field  of  plant  pathology  were 
mycologists  rather  than  bacteriolo- 
gists and  would,  from  choice,  study 
the  fungous  diseases.  (4)  In  the 
diseased  gall  tissue,  comparatively 
few  bacteria  are  present  and  the 
microscope  does  not  conclusively  demonstrate  the  cause  of  the  trouble 
under  ordinary  histological  methods.2 


Fig.  1. — Artificial  inoculations  pro- 
ducing galls  on  Prunus  davidiana. 
This  tree,  known  sometimes  as 
Chinese  ornamental  almond,  has 
been  recommended  as  a  stock  for 
stone  fruits,  but  it  promises  no 
particular  advantage  with  regard 
to  the  crown  gall  disease. 


W.  S.   Department  of  Agriculture,  Bureau  of  Plant  Industry,  Bulletin  No.  213. 

2In  Bulletin  255,  Bureau  of  Plant  Industry,  U.  S.  Department  of  Agriculture,  special  methods  are  described 
for  demonstrating  this  organism  in  the  cell. 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF    CROWN   GALL. 


533 


GENERAL  DESCRIPTION  OF  THE  DISEASE. 

Geographical  Distribution. 

The  disease  is  common  in  every  state  and  territory  of  the  United 
States  j  it  is  found  in  Canada,  South  America,  South  Africa,  the  coun- 
tries of  Europe  and  Asia.  In  other  words,  the  disease  is  nearly  univer- 
sal in  its  distribution  and  almost  omnivorous  as  to  its  choice  of  a  host. 

Galls  or  Knots. 

Galls  or  knots  are  known  to  occur  on  different  parts  of  plants  and 
are  due  to  several  different  causes.  The  one  we  are  considering  is  not 
due  to  any  form  of  insect  and  is  distinct  from  what  is  known  as  the 
knot  of  the  olive,  although  its 
external  characteristics  are 
very  similar.  These  galls  or 
knots  are  more  or  less  spheri- 
cal, somewhat  convoluted  out- 
growths, and  usually  of  rather 
soft,  spongy  tissue,  although 
this  may  eventually  become 
hard.  They  usually  occur  on 
the  stem  and  main  root,  just 
below  the  surface  of  the  soil. 
From  year  to  year  under 
favorable  conditions  they  in- 
crease in  size  and  may  form 
large  excrescences.  However, 
decay  usually  takes  place  and 
the  gall  rots.  This  decay 
may  then  infect  the  tree  and 
be  the  cause  of  its  death. 
Galls  also  occur  to  some 
extent  on  the  secondary  roots, 
even  at  some  distance  from 
the  crown  of  the  tree. 


L  < 

Fig.  2. — Artificial  inoculations  producing 
galls  on  peach,  Prunus  persica.  Peach 
stock  suffers  badly  from  crown  gall. 


Popular  Name. 

The  disease  takes  its  name  from  the  knots  or  galls  produced  and  is 
variably  called  in  literature  Root  Knot,  Crown  Gall,  Black  Knot  or 
Tumors. 

Hosts. 

Natural  knots  have  been  found  on  a  great  variety  of  plants.  The 
following  list,  while  not  supposed  to  be  complete,  will  at  least  show  the 
wide  range  of  plants  subject  to  this  trouble:  Peach,  apricot,  almond, 


534 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


prune,  plum,  apple,  pear,  quince,  English  walnut,  grape,  raspberry, 
loganberry,  cherry,  poplar,  chestnut,  pecan,  California  black  walnut, 

Eastern  black  walnut,  wild  clematis, 
marguerite  or  Paris  daisy,  .honey- 
suckle, Arbutus  unedo,  cotton, 
alfalfa,  beet,  willow,  hop,  red  clover, 
peony. 

Bacterial  Nature  of  Disease. 

There  is  now  abundant  proof 
that  these  knots  are  caused  by  a 
bacterial  organism  that  enters  the 
tissue  through  some  injury,  or  pos- 
sibly at  the  point  where  the  cotyle- 
dons of  such  seeds  as  those  of  the 
stone  fruits  are  attached  to  the 
young  plant.  In  eucalyptus  seed- 
lings the  natural  knots  often  appear 
opposite  each  other  where  the  cotyle- 
dons have  previously  been  attached, 
also  the  quince  knots  appear  first  at 
the  node  about  the  old  leaf  scar.  All 
the  evidence  we  have  goes  to  show 
that  some  injury  or  weakness  is 
necessary  for  infection  to  take  place. 

Prevalence  of  Disease. 

This  disease  is  extremely  common 
in  the  nurseries  of  California.  Peach 
rootstock  is  largely  used,  as  the  pits 
are  easily  and  cheaply  secured  from 
the  canneries  and  the  root  is  well 
adapted  to  the  various  stone-fruit 
trees.  The  amount  of  disease  varies 
from  year  to  year,  being  sometimes  as  great  as  75  per  cent.  This  means 
a  considerable  loss  to  the  nurseryman  and  also  to  the  buyer,  if  the 
nurseryman  is  not  careful  to  cull  out  affected  trees.  Buyers  of  nursery 
stock  cannot  be  too  careful  in  inspecting  their  trees  before  planting, 
and  should  rigidly  live  up  to  the  rule  of  never  planting  a  tree  that  shows 
any  signs  of  small  or  large  knots.  There  are  many  almond,  peach  and 
prune  orchards  that  today  are  unprofitable  because  of  this  disease.  It 
is  impossible  to  give  any  estimate  in  money  of  the  loss  due  to  it  but 
judging  from  the  numerous  inquiries  and  the  correspondence  on  the 
subject  it  must  be  considerable. 


Fig.  3. — -Artificial  inoculations  pro- 
ducing galls  on  Peen-to  hybrid 
peach. 


Bulletin  235]     CATjse   AND   INFECTIOUSNESS   OF    CROWN   GALL. 


535 


PLAN  OF  INVESTIGATION. 


The  importance    of   this    disease    in    California,    and    the    stimulus 
imparted  from  the  knowledge  of  the  results  being  secured  by  Dr.  Erwin 

F.  Smith,  led  us  to  attempt  to   

confirm  and  extend  his  results 
under  local  conditions.  Through 
the  courtesy  of  Mr.  George  C. 
Roeding  of  the  Fancher  Creek 
Nurseries  we  secured  many  of 
the  rootstocks  and  pits  from 
which  we  grew  our  seedlings, 
and,  upon  these,  inoculations 
were  made  with  pure  cultures  of 
bacteria  which  we  succeeded  in 
isolating  from  diseased  peach 
galls. 

Isolation  of  Organism. 

In  the  winter  of  1909  an 
attempt  was  made  to  obtain  the 
crown  gall  organism  from  peach 
knot.  For  this  purpose  diseased 
trees  were  secured  from  a  nur- 
sery, and  the  usual  bacteriologi- 
cal methods  were  employed  to 
secure  pure  cultures  of  any 
organisms  that  might  be  present 
in  these  galls.  From  the  tech- 
nical description  by  Erwin  F. 
Smith  of  Bacterium  tumefaciens, 
we  had  reason  to  expect  that  the 
pathogenic  organism  would  be 
characterized  by  a  pearly  white 
growth  on  nutrient  agar.  A 
large  number  of  transfers  of 
such  colonies  were  made  from 
dilution  plates  and  inoculations 
made  in  small  peach  seedlings. 

Several  different  cultures  were  at  last  secured  that  produced  galls  in 
peach  seedlings.  One  strain  of  these  cultures  was  used  in  all  the  work 
done  in  the  year  1910.  On  February  8,  1911,  fresh  cultures  were  made 
from  artificial  knots  produced  on  Prunus  davidiana  the  previous  year. 


Fig.  4.— Artificial  inoculations  producing 
galls  on  bitter  almond.  Almond  stocks 
are  particularly  susceptible  to  crown 
gall  and  the  trees  are  frequently  killed 
by  it. 


536 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


This  culture  was  used  for  the  most  part  in  the  series  of  inoculations 
carried  out  during  that  year. 

Methods  of  Making  Inoculations. 

All  inoculations  were  made  from  pure  cultures  isolated  from  peach 
root-knots,  unless  otherwise  specified.  A  culture  about  forty-eight  hours 
old  was  used  in  most  of  the  inoculation  work.     A  steel  needle  sterilized 

in  a  gas  flame  was  used  to  transfer  the  growth 
from  the  culture  tube.  In  making  these  inoc- 
ulations the  endeavor  was  to  actually  get  a 
considerable  amount  of  the  bacterial  mass  of 
the  culture  into  the  tissue.  No  attempt  was 
made  to  produce  the  disease  by  applying  the 
germs  to  the  uninjured  surface  of  the  plants, 
and  it  is  very  doubtful  if  this  latter  method 
would  give  anything  but  negative  results. 

In  all  cases,  unless  otherwise  indicated,  the 
inoculations  were  made  above  ground,  on  the 
twigs  or  trunk  of  the  tree  under  experimenta- 
tion. No  protection  against  weather  or  dry- 
ing out  was  made,  and  few  checks  were  used. 
These  were  not  considered  necessary,  as  our 
work  was  far  removed  from  sources  of 
infection,  and  in  many  cases  some  of  the 
punctures  did  not  take  and  could  be  regarded 
as  checks.  Our  purpose  was  chiefly  to  show 
whether  or  not  these  different  stocks  could  be 
made  to  produce  galls. 

It  has  been  stated  that  cultures  of  the  crown 
gall  organism  gradually  lose  their  virulence 
when  grown  on  artificial  media.  To  test  this 
out,  inoculations  were  made  from  one  culture 
which  had  been  used  in  much  of  the  work. 
This  culture,  serial  No.  649,  was  isolated 
December  14,  1909,  and  sub-cultures  made  from  it  from  time  to  time. 
Inoculations  were  made  from  this  culture  on  peach  (a  Peen-to  hybrid) 
on  March  20,  1911,  and  gave  positive  results  January  25,  1912.  A 
further  test  was  made  from  culture  No.  649  on  February  15,  1912. 
Four  branches  of  the  current  year 's  growth  were  puncture-inoculated  on 
the  same  peach  tree  that  was  used  in  1911.  June  21,  1912,  these  showed 
well-developed  galls.  In  these  experiments,  cultures  over  two  years  old 
produced  well-formed  galls. 

In  some  inoculation  work  on  fig,  black  walnut  and  pecan,  at  a  time 


Fig.  5. — Artificial  inocu- 
lations producing  galls 
on  apricot. 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF    CROWN   GALL. 


537 


when  the  trees  were  not  growing  well,  knots  did  not  appear  until  growth 
again  occurred.  The  organism  seemed  to  be  able  to  live  in  the  tissue 
for  a  long  period  without  any  apparent  formation  of  galls,  but  when 
conditions  of  growth  were  again  favorable  the  galls  began  to  develop. 


ARTIFICIAL   INOCULATIONS  OF  PEACH   CROWN   GALL  ON    PRUNUS 
DAVIDIANA.     Fig.   1. 

This  species  has  never  been  used  as  a  rootstock  in  a  commercial  way,  although  it 
has  been  recommended  by  the  United  States  Department  of  Agriculture  as  a  stock  for 
peaches,  almond,  prunes  and  plums  because  of  its  resistance  to  drought  and  alkaline 
soil.  Inoculations  were  at  first  made 
on  branches  of  different  sizes  of  the 
two  varieties  alba  and  rubra.  These 
trees  were  growing  on  the  station 
grounds  and  in  several  instances  the 
inoculated  branch  was  bent  down  and 
covered  with  clean  river  sand.  Small 
seedlings  were  also  inoculated  in  the 
glass  house. 

P.  davidiana  rubra  was  inoculated 
on  June  21,  1910,  on  small  twigs  in 
the  open,  using  a  pure  culture  of  the 
peach  organism.  August  5,  1910, 
indications  of  the  beginnings  of  small 
knots  were  detected.  December  8, 
1910,  observations  were  again  made, 
and  small  but  definite  knots  had  been 
produced.  Further  inoculations  on 
this  species  were  made  on  July  9, 
1910,  on  twigs  one  half  inch  in  diam- 
eter. December  8,  1910,  showed 
medium  sized  galls,  about  one  third 
the  size  of  those  on  peach  (Prunus 
persica).  In  all  this  work  the  galls 
were  smaller  than  on  P.  persica.  Feb- 
ruary 22,  1912,  the  tree  on  which  the 
above  experiments  had  been  conducted 
was  dug  up  and  one  of  the  small  roots 
was  found  to  have  developed  a  very 
large  gall.  Possibly  this  infection 
was  due  to  germs  that  had  been  dis- 
tributed and  found  their  way  into  the 
soil.  The  species  does  not  show  any 
special  immunity  to  this  disease. 

P.  davidiana  alba  was  also  inocu- 
lated on  the  same  dates  and  with  the 
same  cultures  as  was  rubra  and  gave 
fine  galls.  These  seemed  to  be  some- 
what more  readily  produced  on  alba 
than  on  rubra,  but  this  is  without  doubt  due  to  a  difference  in  the  rapidity  of  growth 
of  the  two  trees. 


Fig.  6. — Artificial  inoculations  producing 
galls  on  Myrobolan  plum.  This  is  a 
very  popular  stock  for  various  stone 
fruits  in  California,  but  it  is  susceptible 
to  crown  gall.  ■ 


538  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

Summary  of  results  on  P.  davidiana  alba. 


Date   of   inoculation. 


Result. 


Date  of  observation. 


June  21,  1910 Positive 

June  27,  1910 Positive 

July    1,  1910  Positive 

July    9,  1910  I  Positive 

July  13,  1910  |  Negative 

July  24,  1910  Positive 

July  29,  1910 Positive 

August  6,  1910  Positive 


December  8,  1910 
December  8,  1910 
December  8,  1910 
December  8,  1910 
December  8,  1910 
December  8,  1910 
December  8,  1910 
December  8,  1910 


June  27,  1910,  a  rather  large  branch  was  inoculated  and  immediately  covered  with 
clean  river  sand  that  was  kept  moist.     This  branch  remained  covered  until  August  5, 

1910,  at  which  time  large  knots  had 
developed. 

Experiments  were  made  with  P. 
davidiana  seedlings.  The  pits  were 
obtained  from  the  United  States 
Department  of  Agriculture  by  Dr. 
J.  Eliot  Coit.  They  were  first 
sterilized  with  mercuric  bichloride 
1  :  1000  for  five  minutes,  rinsed  with 
distilled  water  and  then  soaked  for 
three  days  in  water.  Pits  were 
cracked  and  seed  planted  as  follows, 
on  June  24,  1910: 

16  seeds  in  box  having  sterilized 

sand. 
16  seeds  in  box  having  sterilized 

garden    soil. 
16  seeds  in  box  having  unsteril- 

ized  garden  soil. 
25  seeds  in  box  having  unsteril- 
ized  sand. 
The  soil  and  sand  were  sterilized 
for  four  hours  in  autoclave.  Boiled 
water  was  used  for  watering  steril- 
ized soil.  July  14,  1910,  inoculated 
sterilized  sand  with  a  forty-eight 
hour  culture  of  the  knot  organism 
growing  in  Dunham  solution. 
Divided  box  into  two  parts,  one  part 
in  which  the  seedlings  were  injured 
by  making  punctures  with  a  sterile 
scalpel  just  under  the  surface  of  the 
soil,  before  applying  culture  of  knot 
organism.  There  were  seven  trees 
in  this  part  of  the  box.  The  other 
half  contained  ten  uninjured  seed- 
lings, which  were  about  four  inches 
high  at  this  time.  The  two  check 
boxes  of  sand  and  soil  were  un- 
treated. December  13,  1910,  this 
experiment  was  discontinued  and 
showed  the  following  results :  In 
the.  seven  seedlings  that  were 
injured  there  was  one  tree  having  a  gall.  In  the  ten  seedlings  that  were  uninjured 
there  were   two   trees  showing  gall.     In  check  boxes  of  soil   and  sand   there   were 


Fig.  7. — Artificial  inoculations  producing 
galls  on  mahaleb  cherry.  Cherries  are 
not  so  frequently  affected  in  the  orchard 
and  nursery  as  sofne  other  stone  fruits, 
but  they  take  the  disease  readily  from 
artificial  inoculation. 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF    CROWN   GALL. 


539 


thirteen  trees  and  no  gall.  This  experiment  is  not  as  conclusive  as  one  would  expect, 
but  shows  that  the  disease  can  be  transferred  to  small  Prunus  davidiana  seedlings  by 
inoculating  the  soil,  even  if  the  roots  are  uninjured. 


ARTIFICIAL 


INOCULATIONS  OF   PEACH   CROWN   GALL  ORGANISM   ON   PEACH 
(PRUNUS    PERSICA).     Fig.   2. 


The  first  successful  inoculations  were  made  on  March  26,  1910,  upon  small  peach 
seedlings  that  had  been  grown  in  river  sand.  On  May  6th  small  galls  were  observed 
for  the  first  time,  appearing  on  one  of  the  small  peach  seedlings.  This  experiment 
was  repeated  May  12,  1910,  on  three  small  peach  seedlings  with  transfers  of  the  same 


Fig.  8. — Artificial  inoculations  on  English  walnut.  The 
various  walnut  stocks  are  attacked  occasionally  in 
nature,  and  the  disease  can  be  readily  induced  in  any 
of  them  by  introducing  the  specific  bacterium  into 
actively  growing  parts. 


culture.  June  16th  small  galls  were  appearing  on  two  of  the  seedlings ;  the  third  tree 
showed  what  appeared  to  be  the  commencing  of  knots,  but  they  were  not  sufficiently 
definite  to  be  counted.  June  21,  1910,  small  twigs  were  punctured  on  a  tree  in  the 
open  without  protecting  the  wounds  in  any  manner.  August  5,  1910,  fine  positive 
results  showed. 


540 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


SUMMARY  OF  OTHER  SUCCESSFUL  INOCULATIONS  ON  TWIGS  OF  UNKNOWN 
VARIETIES  OF  PRUNUS  PERSICA. 

June  21,  1910,  punctured  2  small  twigs.  Positive  results  December  8,  1910. 
July  9,  1910,  punctured  2  small  twigs.  Positive  results  December  8,  1910. 
Aug.     6,  1910,  punctured  2  small  twigs.     Positive  results  December  8,  1910. 

All  these  inoculations  were  made  on  branches  and  were  in  no  wise  protected.  The 
knots  were  very  large  and  well  developed. 

Peen-to  Peach. 

July  17,  1911,  the  branches  of  a  Peen-to  peach,  commonly  known  as  Australian 
Saucer,  were  inoculated  with  pure  cultures  on  the  small  branches.  On  October  10, 
1911,  small  galls  were  to  be  found.  The  experiment  was  discontinued  at  this  time  as 
the  tree  was  cut  down. 


Fig.   9. — Artificial  inoculations  in  eastern  black 
walnut  A,  in  butternut  B. 
Muir  Peach. 

July  21,  1911,  one  small  seedling  growing  in  the  Station  garden  was  inoculated 
above  ground  on  the  trunk,  and  on  July  31st  three  more  were  puncture-inoculated. 

January  23,  1912,  all  these  inoculations  showed  fine  positive  results,  100  per  cent 
infection. 

Lovell  Peach. 

July  31st  three  Lovell  seedlings  were  puncture-inoculated,  followed  by  three  more 
seedlings  on  August  3,  1911.  January  23,  1912,  there  were  fine  positive  results  in 
almost  every  case. 

Salway  Peach. 

Inoculations  were  made  upon  seedlings  as  follows : 

July    22,  1911,  two  seedlings  inoculated. 

July    31,  1911,  three  seedlings  inoculated. 

Aug.     3,  1911,  two  seedlings  inoculated. 

Aug.   22,  1911,  one  seedling  inoculated. 

Sept.  12,  1911,  one  seedling  inoculated. 


Bulletin  235]     cause   AND   INFECTIOUSNESS   OF    CROWN   GALL. 


541 


On  January  23,  1912,  these  experiments  were  concluded.  In  every  case,  except 
the  September  12th  inoculation,  knots  grew  where  punctures  had  been  made,  showing 
that  this  variety  is  susceptible. 

Peen-to  (Saucer)  Hybrid.     Fig.  3. 

This  is  one  of  the  Florida  saucer  hybrids  that  had  been  grown  in  a  test  of  varieties. 
Inoculations  were  made  March  20,  1911,  with  a  year  old  culture  and  a  more  recently 
isolated  culture  of  the  root-knot  organism.  January  25,  1912,  fine  large  knots  were 
found. 


Fig.    10. — Artificial    inoculations    on 
southern  California  black  walnut. 


Fig.  11. — Artificial 
inoculations  in 
northern  Cali- 
fornia black 
walnut. 


ARTIFICIAL    INOCULATION   OF  PEACH   CROWN   GALL  ORGANISM   ON   ALMOND 

(PRUNUS  AMYGDALUS). 

The  first  experiments  were  made  on  the  twigs  of  a  large  almond  of  the  IXL 
variety  on  July  23,  1910.  These  produced  small,  hard  knots  where  puncture-inocu- 
lated. The  tree  was  not  growing  very  rapidly  at  this  time,  which  may  account  for 
the  small  size  of  the  knots  that  developed. 

Hard  Shell  Almond. 

These  seedlings  were  from  pits  planted  in  a  nursery  row  on  our  Station  grounds. 
They  were  one  to  two  feet  high  when  inoculated  and  continued  to  grow  all  the  fall 
and  most  of  the  winter,  the  leaves  never  falling  until  after  new  growth  commenced  in 
February. 

Inoculations  were  made  as  follows : 
July    15,  1911,  two  seedlings. 
July    22,  1911,  two  seedlings. 
Sept.  15,  1911,  two  seedlings. 


542  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 

January  23d  all  the  above  inoculations  showed  fine  positive  results,  but  the  Septem- 
ber ones  were  much  smaller  than  the  other  galls,  which  were  one  to  two  inches  in 
diameter.     These  galls  were  similar  to  those  shown  in  Fig.  4. 

Bitter  Almond.     Fig.  4. 

The  bitter  almonds  were  fine,  vigorous  seedlings.  They  were  inoculated  on  the 
following  dates : 

July  22,  1911,  one  seedling. 
July  31,  two  seedlings. 

February  23,  1912,  all  these  inoculations  showed  fine  large  knots,  one  to  two  inches 
in  diameter. 

ARTIFICIAL   INOCULATION   OF  PEACH   CROWN   GALL  ORGANISM   ON   APRICOT 
(PRUNUS   ARMENIACA).     Fig.    5. 

Our  first  trial  of  this  stock  was  on  the  twigs  of  the  cultivated  variety  Royal.  It 
was  inoculated  July  23,  1910.  September  1st  there  were  small  hard  knots,  about 
the  size  of  a  sweet  pea  seed.  These  were  observed  from  time  to  time  during  the 
remainder  of  the  year,  but  never  increased  in  size.  They  were  trimmed  off  the 
following  spring. 

Apricot  pits,  variety  unknown,  were  secured  from  the  Fancher  Creek  Nurseries. 
These  were  planted  in  a  nursery  row  in  our  Station  experimental  plot.  The  seedlings 
were  about  one  and  one  half  feet  high  when  puncture-inoculated  on  July  22d  and 
July  31,  1911.  January  15,  1912,  showed  fine  large  knots  on  the  four  seedlings 
experimented  upon.  The  knots  on  these  apricots  are  considerably  larger  than  on  the 
peach  seedlings,  but  not  so  large  as  those  produced  upon  the  hard  and  bitter  almond. 

ARTIFICIAL    INOCULATION    OF    PEACH    CROWN    GALL    ORGANISM    ON    PLUM. 

Fig.  6. 

Our  experiments  were  confined  to  four  sorts,  Myrobolan,  Wickson,  Marianna  and 
German  prune. 

Myrobolan. 

July  3,  1910,  puncture-inoculations  were  made  on  twigs  of  a  tree  about  three  years 
old.  September  1,  1910,  fine  large  galls  had  developed.  Further  experiments  were 
made  on  seedling  stock  growing  in  the  Station  nursery.  June  28,  1911,  two  small 
seedlings,  and  July  17th  one  seedling,  were  inoculated.  November  1,  1911,  these 
showed  galls  one  to  two  inches  in  diameter. 

Marianna. 

Young  seedlings  growing  in  the  Station  nursery  were  inoculated  on  small  branches. 
These  inoculations  were  made  August  3d  and  September  15,  1911.  February  1,  1912, 
small  galls  had  developed  at  every  puncture.  Lateness  in  starting  the  experiment 
readily  accounts  for  the  small  size  of  the  knots,  and  from  our  limited  work  we  regard 
this  sort  of  stock  as  susceptible. 

Wickson  Plum. 

The  inoculations  were  on  a  rather  small  branch  and  were  made  in  a  slightly 
different  manner  from  that  employed  in  other  cases.  Check  punctures  were  first  made 
on  one  branch.  Another  branch  was  then  inoculated  with  a  culture  of  the  organism, 
then  both  were  bent  down  while  still  attached  to  the  tree  and  covered  with  soil  which 
was  kept  rather  moist.  September  16,  1910,  showed  fine  knots  on  inoculated  twig, 
and  none  on  check  branch. 

German  Prune  (Italian  Prune,  Fellenberg). 

For  two  seasons  branches  of  this  tree  have  been  unsuccessfully  puncture-inoculated 
with  cultures  that  were  used  on  other  hosts  with  fine  positive  results.  It  begins  to 
look  as  if  this  particular  tree  might  be  resistant  to  the  peach  organism,  but  further 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF    CROWN   GALL. 


543 


tests  must  be  made  to  be  sure  of  this.  Peach  stock  has  been  budded  to  this  prune 
and  the  new  vigorous  growth  as  well  as  that  on  the  original  tree  will  be  again  tested 
the  coming  season. 

This  work  may  be  summarized  as  follows :  July  23,  1910,  several  puncture  inocu- 
lations were  made  on  branches  of  German  prune ;  September  1,  1910,  negative  results 
were  noted  and  further  observation  on  December  1st  showed  no  knots.  June  28,  1911, 
July  3,  1911,  and  July  17,  1911,  other  puncture-inoculations  on  the  new  growth  of  the 
tree  were  made.  February  24,  1912,  showed  no  indication  of  knots  and  the  tissue 
has  in  nearly  every  instance  healed,  and  is  nice  and  smooth  at  these  points. 


Fig.  12.— Artificial  inoculations  on  pecan. 


ARTIFICIAL    INOCULATION    OF    PEACH    CROWN    GALL   ORGANISM    ON 

CHERRY  STOCK. 

Mazzard. 

These  were  small  trees  secured  from  a  nursery  and  planted  out  in  a  row  in  our 
Station  nursery.     This  stock  seems  to  be  quite  difficult  to  infect. 


June  20,  1911,  inoculated  1  seedling. 

July  17,  1911,  inoculated  4  seedlings. 

July  21,  1911,  inoculated  2  seedlings. 

July  31,  1911,  inoculated  1  seedling. 

Sept.  15,  1911,  inoculated  1  seedling. 


January  23,  1912,  no  galls. 

January  23,  1912,  4  galls  on  1  tree. 

January  23,  1912,  2  galls  on  1  tree. 
January  23,  1912,  no  galls. 
January  23,  1912,  no  galls. 


Mahaleb.     Fig.  7. 

Positive  results  on  this  species  are  greater  in  number  than  on  Mazzard  and  may 
be  summarized  as  follows  : 

June  28,  1911,  inoculated  1  seedling.  January  23,  1912,  no  galls. 
July  12,  1911,  inoculated  1  seedling.  January  23,  1912,  no  galls. 
July    17,  1911,  inoculated  2  seedlings.     January  23,  1912,  galls  on  both. 


544 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


July  21,  1911,  inoculated  2  seedlings. 
July  25,  1911,  inoculated  2  seedlings. 
July    31,  1911,  inoculated  4  seedlings. 


January  23,  1912,  galls  on  both. 
January  23,  1912,  galls  on  both. 
January  23,  1812,  galls  on  all. 


All  these  successful  inoculations  showed  medium  sized  galls,  but  large  enough  so 
there  is  no  question  as  to  their  nature. 

Another  experiment  was  made  on  August  24,  1910.  These  inoculations  were  by 
puncture  on  branches  of  a  two-year-old  tree.  Growth  was  taking  place  slowly. 
July  22,  1911,  knots  found  at  four  of  the  points  of  inoculation. 


Fig.  13. — Artificial  inoculations  on  French  pear  stock. 
Crown  gall  is  not  very  rare  on  pears,  but  it  is  not  by 
any  means  so  common  or  destructive  as  on  the  stone 
fruits.  However,  the  disease  is  very'  readily  induced 
by  artificial  infection  of  this  fruit. 

ARTIFICIAL  INOCULATION  OF  PEACH  CROWN  GALL  ORGANISM  ON  WALNUT. 

Juglans  regia  (English  walnut).     Fig.  8. 

Crown  gall  of  the  English  walnut  has  been  several  times  reported  in  California, 
and  while  the  disease  does  not  appear  to  be  very  widespread,  yet  in  certain  localities 
it  is  found  scattered  through  the  groves.  The  worst  cases  are  where  it  occurs  just 
below  the  surface  of  the  soil.  Here  the  gall  growth  often  seems  to  rot,  probably  due 
to  other  wood-destroying  organisms,  leaving  the  trunk  of  the  tree  often  more  than 
half  eaten  away.    From  observations  thus  far  made,  the  disease  is  far  more  prevalent 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF    CROWN   GALL. 


545 


on  sandy  than  on  other  soils.  In  many  places  the  cutting  out  practice  is  employed, 
the  cut  surface  being  painted  over  with  some  disinfectant,  such  as  a  solution  of 
copper  sulphate,  or  better  still  Bordeaux  mixture.  Ranchers  state  that  they  some- 
times cure  the  disease  by  this  method. 

On  July  29,  1910,  puncture-inoculations  were  made  on  a  small  English  walnut 
branch.  September  2,  1910,  inoculations  were  examined  and  no  gall  formation 
could  be  discovered.  This  experiment  was  regarded  as  discontinued,  but  the  labels 
were  not  removed.  July  19,  1911,  the  writer  again  visited  this  tree  and  was  surprised 
to  find  fine  large  galls  or  tumors. 

In  the  mean  time  other  inoculations  had  been  made  on  the  new  growth  of  an 
English  walnut  tree.  Inoculated  June  3,  1911.  November  14,  1911,  knots  had 
developed  at  every  puncture.  Erwin  F.  Smith  reports  having  secured  positive 
inoculation  of  Juglans  regia  pendula,  but  failed  to  do  so  on  the  straight  English 
walnut. 

Juglans  nigra  (eastern  black  walnut).     Fig.  9A. 

Crown  gall  has  been  before  reported  as  occurring 
on  black  walnut.  Inoculations  were  made  from  the 
same  culture  and  at  the  same  time  as  upon  the  English 
walnut,  July  29,  1910.  No  results  seemed  to  follow 
until  the  following  summer  when  large  knots  were 
found,  July,  1911.  While  this  tree  was  planted  for  a 
straight  Eastern  black,  it  was  of  California  derivation 
and  does  not  seem  to  be  exactly  a  typical  Eastern 
black  walnut.  On  June  7,  1912,  further  inoculations 
were  made  on  an  Eastern  black  walnut  grown  from 
Iowa  seed.  June  27th  showed  knots  as  large  as  a 
sweet  pea  seed. 

Juglans  californica  (southern  California  black 

walnut).  Fig.  10. 
Inoculations  were  made  July  23,  1910,  by  puncture. 
This  experiment  for  the  time  was  overlooked  and  no 
observations  made  until  May  15,  1911.  At  this  time 
there  were  fine,  large,  hard  knots  at  many  of  the 
places  of  inoculation.  These  inoculations  were  made 
on  a  rapidly  growing,  two-year-old  tree.  Another 
inoculation  experiment  made  July  15,  1910,  showed 
positive  results    (large  galls)    December  8,  1910. 

Juglans  californica  variety  hindsii  (northern  Cali- 
fornia black  walnut).     Fig.   11. 

In  one  case  we  found  a  root  of  a  two-year-old 
nursery  tree  having  what  appeared  to  be  typical  crown 
gall.  The  disease  rarely  occurs  on  wild  California 
black  roots.  May  10,  1910,  puncture  inoculations  were  made  on  small  Northern  Cali- 
fornia black  seedlings  that  were  growing  in  a  pot.  August  5,  1910,  small  knots  had 
appeared  at  places  of  puncture.  This  seems  to  indicate  definite  positive  results,  but 
further  inoculations  were  made  on  small  seedlings  on  June  12th  and  July  29th,  1910. 
On  December  8,  1910,  there  were  small  hard  galls  at  points  of  inoculation. 

Professor  R.  E.  Smith  has  observed  large  crown  galls  on  a  Royal  hybrid  (a  hybrid 
between  the  Eastern  and  California  black). 
Juglans  cinerea  (butternut  or  white  walnut).     Fig.  9B. 

A  small  branch  was  inoculated  on  July  29,  1910.  The  gall  did  not  develop  to  any 
extent  until  the  following  spring,  but  in  July,  1911,  small  knots  were  found  where 
punctures  had  been  made.  The  growth  of  this  tree  was  slow,  as  our  conditions  are 
not  favorable  for  the  rapid  growth  of  this  species. 

Juglans  sieboldiana  (Japanese  walnut). 

Inoculations  made  on  July  29,  1910,  had  produced  large  galls  on  July  19,  1911. 
2—235 


Fig.  14.— Artificial  in- 
oculations on  Bartlett 
pear. 


546 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


ARTIFICIAL    INOCULATION    OF   PEACH    CROWN    GALL   ORGANISM    ON    PECAN. 

Fig.  12. 

Inoculations  were  made  on  several  different  dates  on  seedling  pecans  growing  in 
the  Station  nursery.  Unsuccessful  inoculations  were  made  on  July  29,  1910,  August 
24,  1910,  and  September  10,  1910.  This  was  due  to  the  slow  growth  that  the  trees 
were  making. 

August  31,  1911,  pecan  sprouts  were  inoculated  with  pure  culture.  November  16, 
1911,  small  galls  were  beginning  to  appear,  but  the  sprouts  were  accidentally  cut 

down.  September  15,  1911,  a  branch  of  pecan 
was  inoculated  with  pure  culture  of  gall  organ- 
ism. Very  small  galls  were  to  be  observed  in 
the  spring  of  1912,  then  followed  rapid  growth 
of  the  tree,  and  large  galls  resulted,  which 
were  photographed  June  18,  1912.  When  once 
started  in  a  tree,  the  organism  does  not  easily 
lose  its  virulence. 


Fig.  15. — Artificial  in- 
oculations producing 
galls  on  sour  orange. 
Crown  gall  is  very 
readily  produced  on 
various  citrus  species 
by  artificially  intro- 
ducing the  specific 
bacteria  into  actively 
growing  parts,  but  it 
occurs  very  rarely  in 
nature. 


Fig.  16. — Artificial  inocu- 
lations of  B.  tumefaciens 
on  lemon.  Aug.  1,  1911- 
Sept.   30,  1912. 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF    CROWN    GALL. 


547 


ARTIFICIAL    INOCULATIONS    OF    POMACEOUS    TREES    WITH    PEACH    CROWN 

GALL  ORGANISM. 

French  Pear  Stock.     Fig.  13. 

Small  seedlings  were  obtained  from  a  nursery  and  planted  out  in  row  in  our 
Station  experimental  plot.  These  seedlings  were  supposedly  imported,  as  the  heading 
indicates,  from  France.  They  are  probably  of  the  species  Pyrns  communis.  These 
were  inoculated  on  the  rapidly  growing  branches  above  ground.  The  following  is 
the  result  of  work  on  this  stock. 

June  28,  1911,  inoculated  1  seedling.    January  23,  1912,  fine  large  galls. 

July  17,  1911,  inoculated  2  seedlings.     January  23,  1912,  fine  large  galls. 

July  21,  1911,  inoculated  1  seedling.     January  23,  1912,  no  galls  produced. 

July  31,  1911,  inoculated  1  seedling.     January  23,  1912,  fine  large  galls. 

Aug.    1,  1911,  inoculated  3  seedlings.    January  23,  1912,  all  showed  large  galls. 

Most  of  these  inoculations  were  positive,  many  producing  large  galls,  and  in  some 
cases  these  have  developed  without  much  apparent  growth  in  length  of  the  inoculated 
branch.     In  some  cases  the  galls  were  partly  buried  with  soil  by  cultivation. 


Fig.  17. — Artificial  galls  produced 
on  fig.  Crown  gall  has  not 
been  found  growing  naturally 
on  the  fig. 


Fig.  18. — Artificial  galls  produced  on  rose. 


Bartlett  Pear.     Fig.  14. 

Inoculations  were  made  on  rapidly  growing  branches  July  9,  1910.  September  1, 
1910,  there  were  fine  large  knots  at  the  points  of  inoculation.  Dr.  E.  F.  Smith1 
speaks  of  the  Bartlett  as  being  especially  susceptible  to  the  knot,  and  all  the  pear 
stock  thus  far  tested  seems  to  be  very  favorable  for  the  formation  of  galls. 

Chinese  Wild  Pear  (Pyrus  sp.) 

This  was  from  seed  secured  from  the  California  State  Board  of  Horticulture  by 
Professor  E.  B.  Babcock.  Only  one  seedling  was  secured  and  this  was  planted  in 
the  open.  The  branches  were  inoculated  on  August  1,  1911.  January  23d  the 
experiment  was  discontinued.  Medium  sized  knots  had  developed.  The  species  is 
probably  P.  pashia. 


'Crown  Gall  of  Plants,  U.  S.  Department  of  Agriculture,  Bureau  of  Plant  Industry,  Bulletin  213,  p.  44. 


548 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


Apple. 

Very  little  work  has  been  done  in  experimenting  upon  apple  stock  in  an  endeavor 
to  find  a  resistant  root.  The  disease  does  not  seem  to  be  as  important  in  this  State 
upon  apple  as  upon  the  various  stone  fruits.  Mr.  Hedgcock,2  in  his  exhaustive  study 
of  the  apple  gall,  showed  that  certain  varieties  have  some  resistance.  Our  inocula- 
tions, July  29,  1910,  were  on  the  White  Winter  Pearmain,  being  made  in  the  small 
branches  with  pure  forty-eight  hour  cultures  of  the  peach  gall  organism.  The  galls 
developed  much  more  slowly  than  on  most  of  the  hosts  experimented  upon,  but  small 
hard  knots  were  at  length  produced.  Further  inoculations  were  made  on  August  24, 
1910,  and  these  also  gave  positive  results,  as  small  hard  galls. 


Fig.  19. — Artificial  inoculations  in  pepper  tree. 
Angiers  Quince. 

June  3,  1911,  a  vigorous-growing  sprout  of  the  current  year's  growth  was  inocu- 
lated. July  17,  1911,  further  puncture  inoculations  were  made.  Up  to  January  23, 
1912,  no  knots  had  been  found.  No  further  observations  were  recorded  until  July  16, 
1912,  when  small  knot-like  galls  from  one  sixteenth  to  one  eighth  of  an  inch  in  height 
were  observed  to  be  forming  in  the  healed-up  tissue  of  the  old  scars  of  the  inoculation 
of  June  3,  1911.  This  tree  also  has  what  is  belived  to  be  the  regular  aerial  form  of 
quince  knot,  described  on  another  page.  These  are  developing  at  the  nodes  on 
the  older  wood  as  small  prominences,  but  do  not  exactly  resemble  those  developing 
from  the  artificial  inoculations  with  the  peach  gall  organism.  No  natural  knots  have 
been  found  on  the  inoculated  branches. 


2U.   S.   Department  of  Agriculture,   Bureau  of  Plant  Industry,  Bulletin  186. 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF    CROWN    GALL. 


549 


Loquat. 

Inoculations  have  been  tried  on  this  host  several  times  and  always  with  negative 
results,  probably  due  to  the  slow  growth  of  the  tree.  Inoculation  made  September  12, 
1911,  seemed  to  show  the  beginning  of  small  knots,  but  later  observation  on  June  20th 
showed  the  results  to  be  negative. 

INOCULATION  OF  PEACH   CROWN   GALL  ORGANISM   ON  CITRUS. 

Valencia  Orange. 

Inoculations  were  made  on  two  small  twigs  on  August  1,  1911.  Three  knots 
developed.  Two  of  these  were  small  but  the  third  one  was  a  medium-sized  knot  on 
January  23,  1912.  These  increased  in  size  during  the  spring  months  of  1912,  owing 
to  the  active  growth  of  the  tree,  and  on  September  23,  1912,  showed  well-developed 
galls. 


:'-■■  :^;';.-A  -^ 

Jjl 

1 

Fig.  20. — Artificial  inoculations  pro- 
ducing galls  on  branch  of  Victoria 
bottle  tree. 


Fig.  21. — Artificially  caused  galls  on  forest 
red  gum  (Eucalyptus  tereticornis) .  Crown 
gall  has  not  been  known  to  attack  the 
various  species  of  Eucalyptus  in  nature. 
The  significance  of  swellings  found  fre- 
quently at  the  crown  of  young  gum  trees 
is  not  yet  understood.  They  do  not  appear 
to  be  detrimental  to  the  tree. 


Sweet  Lime. 

Inoculations  were  made  at  the  same  time  and  with  the  same  culture  as  those  in 
Valencia  orange.  January  15,  1912,  no  galls  were  observed,  but  March  1,  1912, 
showed  the  beginnings  of  small  galls. 

Sour  Orange.     Fig.  15. 

These  artificial  inoculations  were  made  on  August  1,  1911.     The  observations  of 
March  1,  1912,  showed  small,  but  definite  gall  formation. 
Lemon.     Fig.  16. 

Two  twigs  of  lemons  were  also  inoculated  on  August  1,  1911,  but  on  March  1, 
1912,  no  galls  had  developed.     On  June  21,  1912,  medium  sized  galls  had  formed. 


550 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


ARTIFICIAL    INOCULATION    OF   PEACH    CROWN   GALL  ORGANISM   ON    MISCEL- 
LANEOUS FRUIT-BEARING  TREES. 

Fig  (Ficas  carica).     Fig.  17. 

A  fig  tree  was  inoculated  on  two  branches  August  24,  1910.     Observations  were 
taken  at  various  times  and  no  galls  developed  until  early  in  1912.     At  first  there  were 


Fig.  22. — Artificial  inoculations  on  oleander.     Similar  galls  are  occasionally- 
found  in  abundance,  occurring  naturally. 


only  slight  prominences  that  could  scarcely  be  taken  for  galls.  The  particular 
branches  that  were  inoculated  had  not  been  growing  well  and,  to  stimulate  new 
growth,  were  cut  off  just  beyond  where  the  inoculations  had  been  made.     February  22, 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF    CROWN   GALL.  551 

1912,  one  branch  showed  one  fine  large  knot  and  several  smaller  ones.  June  18,  1912, 
this  branch  was  cut  off  and  photographed.  The  other  inoculated  branch,  on  June  15, 
1912,  showed  one  small  knot.  The  tree  may  be  growing  fast  in  some  parts,  but  if  the 
branch  inoculated  is  not  growing  there  is  little  or  no  gall  formation. 

Muscat  Grapes. 

July  29,  1910,  inoculations  were  made  on  two-year-old  and  present  year's  growth. 
September  1,  1910,  a  small,  knot-like  growth  had  developed  at  each  puncture.  The 
vines  were  not  making  very  rapid  growth  at  this  time  and  because  of  this  the  knots 
produced  were  small  but  large  enough  to  indicate  positive  results. 

Avocado. 

Experiments  have  been  tried  on  but  one  tree  and  that  has  not  been  growing  very 
rapidly.    These  were  made  in  August,  1910,  but  did  not  produce  galls. 

Olive. 

July  29,  1910,  tested  out  organism  on  olive  shoots.  September  1,  1910,  negative 
results.  Other  puncture-inoculations  have  been  made  and  these  gave  negative  results. 
These  results  agree  with  those  of  E.  F.  Smith. 

Cherimoya  (Anona  cherimolia). 

Inoculations  were  made. on  rapidly  growing  seedlings  on  July  31,  1911.  February 
29,  1912,  no  knots  had  been  produced. 

INOCULATIONS  OF  PEACH    CROWN    GALL   ORGANISM   ON   SOME 
ORNAMENTAL  TREES. 

Relatively  little  is  known  regarding  crown  gall  on  ornamental  trees  and  shrubs, 
and  while  the  work  thus  far  done  is  only  a  beginning  in  testing  out  these  many 
different  species  yet  the  results  secured  deserve  mention. 

Rose.     Fig.  18. 

An  unknown  variety  of  climbing  rose  was  inoculated  August  24,  1910.  February  1, 
1911,  the  experiment  was  discontinued.     Fine  large  knots  had  developed. 

Catalina  Cherry  (Prunus  integrifolia). 

These  plants  were  grown  from  seed  and  when  about  six  months  old  were  inoculated. 
Few  galls  developed,  owing  to  slow  growth  at  time  of  inoculation. 

July  17,  1911,  inoculated  2  seedlings.  February  23,  1912,  1  knot. 
July  22,  1911,  inoculated  1  seedling.  February  23,  1912,  0  knot. 
July  27,  1911,  inoculated  1  seedling.  February  23,  1912  1  knot. 
Aug.    1,  1911,  inoculated  1  seedling.     February  23,  1912,  0  knot. 

Hill  Cherry  (Prunus  ilicifolia). 

Seedlings  of  the  same  age  as  the  Catalina  cherries.  Inoculations  made  July  12, 
22,  31,  1911.  On  February  23,  1912,  no  galls  had  developed.  Too  slow  growth  for 
knot  development. 

Pepper  Tree  (Schinus  molle).     Fig.  19. 

This  host  is  exceedingly  easy  of  infection.  It  should  also  be  noted  that  even  an 
ordinary  puncture  with  a  sterile  needle  produces  a  slight,  roundish  enlargement  of 
the  healing  tissue,  but  this  is  very  small  as  compared  with  gall  development.  July  29, 
1911,  puncture-inoculations  were  made  on  a  sprout  from  a  large  pepper  tree,  also  a 
branch  was  punctured  with  sterile  needle  as  a  check.  September  1,  1911,  medium 
sized  knots  had  developed  from  the  inoculations.  Similar  inoculations  were  made  on 
July  31,  1911.  on  a  small  pepper  seedling.  Large  knots  had  finally  developed  when 
the  experiment  was  discontinued  on  January  23,  1912. 


552 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION. 


Victoria  Bottle  Tree  (Sterculia  diversifolia).     Fig.  20. 

A  small  seedling  was  inoculated  on  October  19,  1910,  also  on  August  3,  1911.  In 
both  cases  knots  developed  very  readily  at  points  of  puncture.  The  small  twigs  of  a 
small  tree  were  inoculated  on  September  9,  1911.  On  March  25,  1912,  these  inocula- 
tions gave  definite  knots  at  almost  every  puncture. 

Flame  Tree    (Sterculia  acerifolia). 

A  small  seedling  growing  in  pot  was  inoculated  on  December  12,  1911.  Growth  of 
plant  slow,  but  on  March  25th  the  beginnings  of  small  knots  were  to  be  observed. 

Forest  Red  Gum  (Eucalyptus  tereti- 
cornis).     Fig.    21. 

Seedlings  of  four  to  six  feet  were  inocu- 
lated. The  first  successful  inoculations 
were  made  May  16,  1910.  On  March  25, 
1912,  there  was  one  large  knot  and  one 
very  small  one  at  points  of  inoculation. 
September  2,  1911,  inoculated  a  seedling 
about  one  half  inch  in  diameter.  Febru- 
ary 20,  1912,  there  were  two  small  knots. 
On  March  26,  1912,  one  of  these  knots 
had  grown  rapidly  in  size,  the  other  had 
not  changed. 

Inoculations  were  made  on  small  seed- 
lings July  29,  1910,  on  the  branches. 
Typical  roundish  knots  or  galls  had 
developed  on  September  5,   1910. 

Silk    Oak    (Grevilliea    robusta). 

Inoculations  have  been  made  on  the 
branches  of  silk  oak  trees  in  the  open 
at  various  times  but  thus  far  have  only 
given  negative  results.  This  is  probably 
due  to  the  slow  growth  of  the  tree. 

The  several  workers  of  the  Bureau  of 
Plant  Industry  have  published  their 
results  from  inoculating  various  hosts 
with  the  peach  gall  organism.  They 
secured  positive  inoculations  on  the 
following  plants :  Daisy,  Pelargonium, 
peach,  apple,  raspberry,  rose,  sugar  beet, 
and  hop.  Negative  results  are  recorded 
on  olive,  phlox,  verbena,  grape,  impatiens, 
magnolia,  peony,  red  oak,  Persian  walnut 
and  tradescantia.  It  should  be  stated 
that  unfavorable  conditions  in  many  cases 
would  explain  many  of  the  negative 
results  above  recorded. 


Fig.    23. 


-Knot   found    on    lemon,    nearly 
natural  size. 


The  workers  referred  to  in  the  above  paragraph  have  also  isolated  and  studied 
organisms  from  knots  on  the  following  hosts:  Arbutus  anedo,  alfalfa,  sugar  beet, 
cotton,  Paris  daisy,  grape,  honeysuckle,  peach,  quince,  raspberry,  rose. 


OTHER  GALLS  THAT  ARE  AT  PRESENT  LITTLE  UNDERSTOOD. 

Pecan  Gall. 

There  is,  so  far  as  known,  no  record  of  crown  gall  occurring  on  pecans,  but  on 
May  25,  1910,  while  examining  some  pecan  trees  that  had  been  planted  on  the  Whittier 
Station  grounds  for  about  three  years,  a  large  gall  was  found  on  one  of  the  trees 
just  below  the  surface  of  the  soil.     A  portion  of  the  diseased  tissue  was  removed  and 


Bulletin  235]     CAUse   AND   INFECTIOUSNESS   OP   CROWN   GALL. 


553 


cultures  made  from  the  material.  The  appearance  of  the  colonies  and  growth  seemed 
to  be  typical  of  Bacterium  tumefaciens.  Inoculations  were  made  with  transfers  from 
these  colonies  on  peach,  June  27,  1910.  August  6,  1910,  showed  characteristic  gall 
formation.     No  further  study  was  made  of  this  strain. 

Lemon  Gall.     Figs.  23  and  24. 

This  gall  is  not  common,  but  has  been  found  a  few  times  on  the  branches  by 
Professor  H.  S.  Fawcett,  who  has  figured  and  described1  it.  The  writer  is  under 
special  obligation  to  Mr.  Fawcett  for  lemon  gall  material  which  he  furnished  for  cul- 
tural work  and  study.  Culture  from  the  lemon  gall  in  prune  juice  gave  only  negative 
results,  while  cultures  in  standard  nutrient  agar  seem  to  give  characteristic  colonies 
of  Pacterium  tumefaciens.     Work  is  still  in  progress  in  their  study. 


Fig.  24. — A  medium  sized  gall  on  lemon,  reduced. 


Orange  Knot.     Figs.  25  and  26. 

Some  aerial  galls  were  found  on  a  navel  orange  tree  but  are  of  rare  occurrence, 
having  been  found  on  but  two  occasions.  Cultures  made  in  prune  juice  and  nutrient 
glucose  agar  failed  to  show  any  fungous  growth  that  could  be  regarded  as  significant. 
From  the  work  thus  far  done,  it  does  not  seem  to  be  due  to  Sphwropsis  tumefaciens.2 
In  nutrient  agar  colonies  appeared  that  closely  resemble  those  of  Bacterium  tume- 
faciens. At  present  it  is  impossible  to  say  what  the  cause  of  the  knots  may  be,  but 
work  is  still  being  done  on  this  problem. 

Eucalyptus  Knot. 

Galls  occur  frequently  on  the  small  seedlings.  These  are  hard  knots  that  occur 
always  at  the  nodes.     There  will  often  be  a  gall  on  each  side  of  the  plant  where 


1The  Monthly  Bulletin  of  State  Commission  of  Horticulture,  October,  1912. 
2U.  S.  Department  of  Agriculture,  Bureau  of  Plant  Industry,  Bulletin  247. 


554 


UNIVERSITY   OF   CALIFORNIA — EXPERIMENT    STATION. 


cotyledons  or  the  opposite  leaves  have  previously  been.  We  have  had  small  seedlings 
with  these  natural  galls  under  observation  for  about  three  years.  In  some  cases 
there  is  an  increase  in  size  in  the  knots,  which  still  continue  to  be  hard  and  do  not 
in  any  way  appear  to  weaken  the  trees.     In  many  cases,  the  diseased  trees  have  com- 


FlG. 


-Small  aerial  gall  on  navel  orange  branches. 


pletely  outgrown  the  disease  and  in  these  instances  there  has  been  but  little  increase 
in  size  of  original  knots.  From  our  observations  the  disease  does  not  seem  to  seriously 
injure  the  growth  of  the  tree.  Numerous  attempts  to  isolate  a  pathogenic  organism 
have  resulted  in  failures,  although  we  still  believe  the  galls  may  be  caused  by  such  an 
organism. 


Quince.     Figs.  27  and  28. 

The  very  abundant  galls  on  quince  branches  in  California  are  quite  different  in 
appearance  from  the  knots  that  we  have  thus  far  considered,  namely  those  of  the 
apple,  peach,  pear,  and  plum.  The  knots  as  they  are  found  on  young  quince  trees  are 
small  roundish  prominences,  usually  several  at  a  node  and  near  the  old  leaf  scar  or  at 


Bulletin    2  35]       CAUSE   AND   INFECTIOUSNESS   OF   CROWN    GALL. 


555 


the  base  of  a  branch.  In  more  advanced  stages  on  old  twigs  the  knots  are  rough  or 
warty  outgrowths  and  always  near  a  node,  or  at  the  base  of  a  branch.  The  effect  of 
these  knots  on  the  tree  is  not  often  serious,  and  it  is  next  to  impossible  to  find  an  old 
quince  tree  in  California  that  is  free  from  them.  The  very  commonness  of  this 
condition  would  lead  us  to  question  whether  it  could  be  caused  by  a  pathogenic 
organism.  Thus  far  cultures  made  from  the  small  natural  gall  on  quince  have  not 
given  a  pathogenic  organism.  Cultures  recently  made  from  a  large  aerial  quince  gall 
have  produced  an  organism  that  is  pathogenic  on  Royal 
apricot.  These  inoculations  were  made  May  1,  1912, 
and  good-sized  galls  were  fouDd  by  July  10,  1912.  The 
galls  are  round  and  smooth  and  do  not  seem  to  agree 
very  well  with  those  obtained  by  Dr.  Erwin  F.  Smith  in 
his  work  with  the  quince  organism,  as  he  secured  rather 
warty   outgrowths. 


JL 

v.*  *-S^^r  •': 

~~-3J|M|^HflnHsL^. 

V^W" 

I  t                        1% 

'"*^^  .3^1 

I 

Fig. 


26. — A  large  gall  of  orange  reduced  to  about  one 
fourth  natural  size. 


Fig.  27. — Small  galls  as 
they  occur  on  quince 
branches.  These  repre- 
sent the  early  stages  of 
the  galls  shown  in  Fig. 
28. 


Clematis  Gall. 

Galls  were  found  on  one  of  our  species  of  wild  Clematis  at  a  place  where  nothing 
but  the  wild  plant  had  ever  grown.  The  appearance  of  the  knots  seemed  to  be  similar 
to  those  caused  by  the  tumefaciens  organism  and  could  not  be  confused  with  nematode 
or  insect  galls.  Also  it  should  be  noted  that  a  recent  bulletin*  of  the  Bureau  of  Plant 
Industry  illustrated  natural  galls  on  the  branch  of  mesquite,  a  wild  shrub.  It  has  not 
definitely  been  proved  that  this  is  due  to  bacteria  but  in  appearance  it  resembles  those 
that  have  been  so  produced. 


»TJ.   S.    Department  of  Agriculture,  Bureau  of  Plant  Industry.  Bulletin  226,  Plate  XV. 


556  UNIVERSITY    OF   CALIFORNIA — EXPERIMENT    STATION. 


Fig.   28. — Large  rough  galls  on  the   nodes  of  quince   branches. 
These  galls  have  not  yet  been  adequately  studied. 

SUMMARY  AND  CONCLUSIONS. 

1.  Bacterium  tumefaciens  is  native  to  many  of  the  California  soils  and 
causes  losses  in  the  nurseries  that  sometimes  amount  to  70  per  cent. 

2.  Galls  can  be  produced  on  many  different  kinds  of  trees  above 
ground  when  artificial  puncture-inoculations  are  made  with  pure  culture 
of  the  bacterium. 

3.  The  following  trees  have  been  successfully  infected:  several 
varieties  of  peach;  Prunus  davidiana;  bitter  and  hard-shell  almond; 
apricot;  Myrobolan,  Marianna  and  Wickson  plum;  Mazzard  and 
Mahaleb  cherries ;  the  English  walnut ;  Japanese,  Eastern  and  California 
black  walnuts;  pecan;  French  pear  stock;  Bartlett  and  Chinese  wild 
pear;  apple;  Angiers  quince;  sour  and  sweet  (Valencia)  citrus  stock; 


Bulletin  235]     CAUSE   AND   INFECTIOUSNESS   OF   CROWN   GALL.  557 

sweet  limes  and  lemons ;  fig ;  Muscat  grapes ;  eucalyptus ;  Victoria  bottle 
tree ;  flame  tree ;  oleander ;  pepper  tree ;  and  Prunus  integrifolia  ( Cata- 
lina  cherry) . 

4.  The  following  have  been  puncture-inoculated  but  have  always  given 
negative  results:  loquat;  Grevilliea  robust  a  (silk  oak)  ;  German  prune; 
Prunus  ilicifolia  (wild  hill  cherry)  ;  Anona  cherimolia;  avocado ;  olive. 
Some  of  these  are  being  further  tested  and  may  not  prove  to  be  resistant. 

5.  Characteristic  aerial  galls  occur  on  different  kinds  of  trees  in  Cali- 
fornia, the  cause  of  which  has  not  been,  in  all  cases,  demonstrated. 
These  knots  resemble  closely  those  produced  by  the  crown  gall  organism. 

6.  The  trees  in  California  thus  far  observed  to  have  aerial  galls  are 
the  quince,  olive,  lemon,  sweet  orange,  oleander  and  grape. 

7.  The  aerial  galls  of  the  olive  and  grape  have  been  carefully  studied 
and  their  cause  determined.  The  remainder  are  being  studied,  but  are 
at  present  not  well  understood. 


STATION    PUBLICATIONS    AVAILABLE    FOR    DISTRIBUTION. 

REPORTS. 

1896.  Report  of  the  Viticultural  Work  during  the  seasons  1887-93,  with  data  regard- 

ing the  Vintages  of  1894-95. 

1897.  Resistant  Vines,   their  Selection,  Adaptation,  and  Grafting.     Appendix  to  Viti- 

cultural Report  for  1896. 

1902.  Report  of  the  Agricultural  Experiment  Station  for  1898-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for  1901-03. 

1904.  Twenty-second  Report  of  the  Agricultural  Experiment  Station  for  1903-04. 


BULLETINS. 


Reprint. 
No.   128. 

133. 

147. 

162. 

164. 

167. 

168. 

169. 

170. 
171. 

174. 
176. 


177. 


178. 
179. 


181. 
182. 


183. 
184. 

185. 

186. 

187. 

188. 

189. 

191. 
192. 

194. 

195. 

197. 


Endurance  of  Drought  in  Soils 
of  the  Arid  Regions. 

Nature,  Value,  and  Utilization  of 
Alkali  Lands,  and  Tolerance 
of  Alkali.  (Revised  and  Re- 
printed, 1905.) 

Tolerance  of  Alkali  by  Various 
Cultures. 

Culture  Work  of  the  Sub-sta- 
tions. 

Commercial  Fertilizers.  (Dec. 
1,   1904.) 

Poultry  Feeding  and  Proprie- 
tary Foods. 

Manufacture  of  Dry  Wines  in 
Hot  Countries. 

Observations  on  Some  Vine 
Diseases  in  Sonoma  County. 

Tolerance  of  the  Sugar  Beet  for 
Alkali. 

Studies  in  Grasshopper  Control. 

Commercial  Fertilizers.  (June 
30,   1905.) 

A  New  Wine-cooling  Machine. 

Sugar  Beets  in  the  San  Joaquin 
Valley. 

A  New  Method  of  Making  Dry 
Red  Wine. 

Mosquito  Control. 

Commercial  Fertilizers.  (June, 
1906.) 

The  Selection  of  Seed- Wheat. 

Analyses  of  Paris  Green  and 
Lead  Arsenate.  Proposed  In- 
secticide Law. 

The  California  Tussock-moth. 

Report  of  the  Plant  Pathologist 
to  July  1,  1906. 

Report    of    Progress    in 
Investigations. 

The  Oidium  of  the  Vine. 

Commercial  Fertilizers, 
ary,   1907.) 

Lining    of    Ditches    and 
voirs      to      Prevent 
Losses. 

Commercial  Fertilizers.  (June, 
1907.) 

California  Peach  Blight. 

Insects  Injurious  to  the  Vine  in 
California. 

Commercial  Fertilizers.  (Dec, 
1907.) 

The  California  Grape  Root- 
worm. 

Grape  Culture  in  California ; 
Improved  Methods  of  Wine- 
making  ;  Yeast  from  California 
Grapes. 


Cereal 


(Janu- 

Reser- 
Seepage 


No.  198. 
199. 
201. 

202. 

203. 

204. 

205. 

206. 

207. 

208. 
209. 
210. 

211. 

212. 
213. 
214. 
215. 

•        216. 


217. 
218. 
219. 

220. 

221. 

222. 
223. 
224. 

225. 

226. 
227. 
228. 

229. 

230. 
231. 

232. 
233. 


234. 


The  Grape  Leaf-Hopper. 

Bovine  Tuberculosis. 

Commercial  Fertilizers.  (June, 
1908.) 

Commercial  Fertilizers.  (De- 
cember,  1908.) 

Report  of  the  Plant  Pathologist 
to  July  1,  1909.) 

The,  Dairy  Cow's  Record  and 
the  Stable. 

Commercial  Fertilizers.  (De- 
cember,   1909.) 

Commercial  Fertilizers.  (June, 
1910.) 

The  Control  of  the  Argentine 
Ant. 

The  Late  Blight  of  Celery. 

The  Cream  Supply. 

Imperial  Valley  Settlers'  Crop 
Manual. 

How  to  Increase  the  Yield  of 
Wheat  in  California. 

California  White  Wheats. 

The  Principles  of  Wine-making. 

Citrus  Fruit   Insects. 

The  Housefly  in  its  Relation  to 
Public   Health. 

A  Progress  Report  upon  Soil 
and  Climatic  Factors  Influenc- 
ing the  Composition  of  Wheat. 

Honey  Plants  of  California. 

California   Plant   Diseases. 

Report  of  Live  Stock  Conditions 
in  Imperial  County,  California. 

Fumigation  Studies  No.  5  ;  Dos- 
age Tables. 

Commercial  Fertilizers.  (Oct., 
1911.) 

The  Red  or  Orange  Scale. 

The  Black  Scale. 

The  Production  of  the  Lima 
Bean. 

Tolerance  of  Eucalyptus  for 
Alkali. 

The  Purple  Scale. 

Grape  Vinegar. 

Pear  Thrips  and  Peach  Tree 
Borer. 

Hog  Cholera  and  Preventive 
Serum. 

Enological  Investigations. 

Walnut  Culture  in  California. 
Walnut  Blight. 

Commercial  Fertilizers. 

Three  Years'  Work  of  the  Fern- 
dale  (Humboldt  County)  Cow 
Testing  Association. 

Red  Spiders  and  Mites  of  Citrus 
Trees. 


CIRCULARS. 


No. 


1. 

7. 

9. 
11. 
29. 


46. 


52. 


55. 

60. 
61. 

62. 


Texas  Fever. 

Remedies  for   Insects. 

Asparagus  Rust. 

Fumigation  Practice. 

Preliminary  Announcement  Con- 
cerning Instruction  in  Practi- 
cal Agriculture  upon  the  Uni- 
versity Farm,   Davis,   Cal. 

Suggestions  for  Garden  Work  in 
California   Schools. 

Information  for  Students  Con- 
cerning the  College  of  Agricul- 
ture. 

Farmers'  Institute  and  Univer- 
sity Extension  in  Agriculture. 

Butter  Scoring  Contest,   1910. 

University  Farm  School. 

The  School  Garden  in  the  Course 
of   Study. 


No.   63.     How    to    Make    an    Observation 
Hive. 

65.  The    California    Insecticide    Law. 

66.  Insecticides    and    Insect    Control. 

67.  Development  of  Secondary  School 

Agriculture  in  California. 

68.  The   Prevention  of   Hog  Cholera. 

69.  The    Extermination    of    Morning- 

Glory. 

70.  Observation  of  the  Status  of  Corn 

Growing  in  California. 

74.  Rice. 

75.  A  New  Leakage  Gauge. 

76.  Hot  Room  Callusing. 

77.  University    Farm    School. 

78.  Announcement  of  Farmers'  Short 

Courses  for  1912. 

79.  List  of  Insecticide  Dealers. 

80.  Boys'  and  Girls'  Clubs. 

81.  Sweet   Pea   Growing  Clubs. 


